Islamic State group claimed responsibility for the terrorist attack that rocked London Friday — the fifth this year — and UK officials raised the terror threat to critical, meaning they expect another attack.

Tourists strolling along the famous Champs-Elysees in Paris, France on Monday afternoon watched in horror as a car rammed into a police van -- and some witnessed the car burst into flames as police grabbed the man inside and put him on the ground.

The British-born suspect is believed to be the assailant who plowed through pedestrians on Westminster Bridge on Wednesday, then ran toward the Parliament compound with a knife, which he used to fatally wound Police Constable Keith Palmer before he was shot and killed by other police.

The killer who knifed to death two French police officials in their home this week, claiming allegiance to the Islamic State group, tracked the couple days before the gruesome murders and uploaded his claim of responsibility on the family computer.

President François Hollande described the killings of the couple — police Capt. Jean-Baptiste Salvaing, 42, and his partner, Jessica Schneider, 36, identified as an administrative secretary at a police department outside Paris — as "undeniably a terrorist attack" and said that "France is confronted by an extremely high terrorist threat."

France's president called Tuesday for increased security in a nation already on high alert after an apparent Islamic State-inspired attacker fatally stabbed a couple with police ties and recorded a message before he was killed by police. More Here.